Lignin is a renewable carbon source and the second most abundant biopolymer next to cellulose on earth. It is a crosslinked and complex natural polymer composed of a phenyl propane unit as a basic unit, and lignin includes about 65 percent carbon, 6 percent hydrogen, and 29 percent oxygen. A great amount of lignin can be obtained from the pulping industry in the name of kraft lignin (or thiolignin) and lignosulfonate (LS). The approximate amount of lignin production in the existing pulping industry worldwide is estimated at more than 50 million tons/year. However, the complex structure of lignin makes the production of value-added chemicals from lignin difficult. Therefore, most lignin is currently not isolated, but is instead burned onsite to recover pulping chemicals and provide steam for power production in kraft pulp mills.
In this respect, LS from the sulfite pulping process is a largely available source of lignin, and the global production of LS is currently around 1 million tons/year. LS has been used for concrete admixtures, dispersants and dust suppression for roads, pellet binders, and vanillin. Others have also attempted to convert lignin into value-added materials, but there are few reports on the successful commercialization of lignin-related products. In particular, there are currently no systematic approaches in the processing of lignin for conversion into carbon-based nanomaterials, including the conversion of lignin to graphene. Additionally, carbon nanomaterials, such as graphene, have stimulated considerable scientific, industrial, and commercial interest due to their intriguing physical properties and enormous potential for various applications. Therefore, it would be beneficial if lignin could be utilized as an alternative carbon source for the production of high value carbon-based nanomaterials and the like.
Accordingly, there remains a need for systems and methods that can convert lignins and/or sources thereof to carbon nanomaterials, such as graphene. It would be advantageous if systems and methods could be achieved to convert lignins to carbon nanomaterials using simple and cost effective solutions.